Methyl formate is an extremely important intermediate in C1 chemistry, with a wide range of applications. Products such as formic acid, formamide, N, N-dimethylformamide, dimethyl carbonate, ethylene glycol, acetic acid, methyl acetate, acetic anhydride, methyl methacrylate, high purity CO, diphosgene and the like can be synthesized from methyl formate. Methyl formate can also be used as insecticides, pesticides, fumigants and tobacco processing agents. The consumption of methyl formate comprises as follows: synthetic leathers accounting for 30%, pesticides accounting for 26%, pharmaceuticals accounting for 25%, acrylonitrile accounting for 10%, others accounting for 9%. With the development of polyacrylonitrile fibers, polyurethane synthetic leathers, pharmaceutical industries and the like, the market demand for methyl formate will grow at a rate of 10% per annum.
Processes for producing methyl formate mainly include: methanol-formic acid esterification, liquid-phase methanol carbonylation, dehydrogenation of methanol, oxidative dehydrogenation of methanol, formaldehyde dimerization, direct synthesis from syngas, etc. Among them, industrialized processes are methanol-formic acid esterification, liquid-phase methanol carbonylation and dehydrogenation of methanol. Methanol-formic acid esterification has been eliminated because of backward technology, high energy consumption and serious equipment corrosion. As a new technology at present, dehydrogenation of methanol has not yet been applied in large scale industries. Currently liquid-phase methanol carbonylation is the main process used in industry. Since 1982, almost all of new plants in the world have been employing the technology of liquid-phase methanol carbonylation, which has become the main process for mass production of methyl formate.
Liquid-phase methanol carbonylation (CH3OH+CO=HCOOCH3) was first industrialized by BASF corporation, Germen, the only industrialized catalyst is sodium methoxide whose significant advantage is high selectivity, and methyl formate is the only product. However, the following serious disadvantages exist in using the sodium methoxide catalyst: (1) sodium methoxide is extremely sensitive to water, thus the demand for the purity of raw material is very high, wherein the contents of impurities such as H2O, CO2, O2, sulfides and the like should be less than 10−6, and water content in methanol should also be less than 10−6; (2) sodium methoxide is a strong base and is severely corrosive to equipment; (3) the reaction is carried out in reaction kettle and belongs to homogeneous reaction, wherein the separation of catalyst from product is difficult; (4) the pressure of reaction is relatively high, which is about 4 MPa; (5) the solubility of sodium methoxide in methyl formate is relatively small, if, after the conversion of methanol was greater than a certain limit value, the sodium methoxide will form solid precipitate which will clog pipes and valves, bringing great difficulties to practical operation, and even normal production will be impossible.
Given the defects existing in the current process of liquid-phase methanol carbonylation, the present application discloses a process for vapor-phase methanol carbonylation to methyl formate and a catalyst used in the process. Methyl formate is synthesized on a supported nano-scaled platinum group metal heterogeneous catalyst instead of the sodium methoxide catalyst. The process and the catalyst disclosed by the present application have solved the technical problems in current industrial technology, such as high requirements for purity of raw materials, a severe corrosion of the equipment by a catalyst, a difficulty in separation for a catalyst from a product, a high reaction pressure, great difficulties in operation and so on, and provide a novel technical route for producing methyl formate.